Final answer:
Fungi produce oxalic acid, which contributes to the biodeterioration of stone building materials by reacting with minerals like calcite and causing chemical weathering.
Step-by-step explanation:
The production of oxalic acid by fungi is thought to be a major contributor to the biodeterioration of stone building materials. Fungi metabolize various substances and can produce oxalic acid as a byproduct. This oxalic acid can then react with certain minerals in stone, such as calcite in marble and limestone, leading to chemical weathering. This issue is magnified in conjunction with other forms of acid damage, such as that caused by acid rain from industrial pollution. The acid rain, often containing sulfuric acid, further exacerbates the deterioration of these materials.